Redundancy among environmental quality metrics of streams in an agricultural landscape

Abstract

Biological indicators are widely used for the evaluation of the environmental quality of waterbodies. Since monitoring involves high sampling costs, and the creation of multimetric indices assumes uncorrelated metrics, this study evaluated whether there was correlation among metrics that characterize land use and cover, riparian zone composition and forest structure, as well as correlations among indicators of macroinvertebrate and fish communities. The study was conducted on 12 low-order tributaries of the Jacaré-Pepira and Jacaré-Guaçu Rivers, forming a gradient of environmental stress in the central region of São Paulo State. There were no correlations among land use metrics, and only pasture cover was correlated with some metrics of riparian forest structure. Therefore, both information on land use and riparian composition and forest structure can be important in the environmental assessment of streams. All metrics related to macroinvertebrate communities were correlated to each other, as well as most metrics related to fish communities, although most studies proposing multimetric indices have not found correlation among these metrics. Those studies evaluated streams in extreme situations (preserved vs. impacted), and impacted streams were influenced by different degradation drivers, which may result in distinct responses by the biological communities. The results of the present study suggest that the development of indices must be specific to the studied region, and that frequently the evaluations are carried out in relation to specific drivers of impact, which may vary for different systems.